Those close to the World Trade Center on Sept. 11, 2001 have stronger memories of the terrorist attacks than do those who were in other parts of New York City on that day, according to a study by researchers at New York University, Harvard University, and Rutgers University. The results, which indicate personal involvement may be critical in producing certain memories, are reported in the most recent issue of the Proceedings of the National Academy of Sciences.
“Although all of the study’s subjects were in Manhattan on 9/11, the recollections of those who were in lower Manhattan, close to the World Trade Center, were qualitatively different from those who were further away,” said NYU Professor Elizabeth Phelps, the study’s lead researcher. “The downtown subjects reported seeing, hearing, and smelling what had happened. Subjects who were, on average, around midtown Manhattan reported experiencing the events second hand, such as on television or the Internet. It is clear from these recollections that proximity to the World Trade Center changed the nature of the experience of these events, such that those subjects who were downtown on 9/11 had greater personal involvement with the consequences of the terrorist attacks.”
The findings also raise questions about the psychological concept “flashbulb memory.” The concept, originally based on findings of people’s memories of the assassination of John F. Kennedy, maintains that unique mnemonic processes are involved in creating memories for shocking, public events. Flashbulb memory posits that, similar to a camera’s flashbulb, the surprising and consequential nature of these events triggers a mechanism that conserves what occurred at that instant, producing a picture-like representation, commonly called a “flashbulb” memory.
However, the findings on 9/11 memories indicate that personal involvement may be critical in producing memories with the characteristic qualities of flashbulb memories. This is because the researchers found that the amygdala, a small almond shaped structure in the brain that is vital in enhancing the feeling of remembering emotional material, was activated only for subjects who were in lower Manhattan, near the World Trade Center, on Sept. 11, 2001. By contrast, subjects as little as five miles away-in mid-town Manhattan-did not reveal amygdala involvement.
A video of Phelps discussing other findings pertaining to memories of 9/11 may be viewed at http://www.nyu.edu/about/video.spotlight.html (see video titled “Memories of 9/11”).
NYU houses a database of memories of 9/11 from across the United States. A week after the Sept. 11 attacks, researchers from a consortium of institutions around the country began surveying Americans in order to comprehend how the public understood and recalled the 2001 tragedy. Follow-up surveys were administered in two subsequent years, 2002 and 2004, leaving the consortium with recollections of hundreds of those who lived through 9/11 as they remembered it shortly after that fateful day and years later. The database will be open for general scholarly use in approximately 3 years. For more information on the project and sample surveys, go to http://911memory.nyu.edu/
Methodology and Findings
The study, conducted approximately three years after the 9/11 terrorist attacks in Manhattan, included twenty-four participants who were in New York City on that day. Participants were divided into two groups: the downtown group (those close to the World Trade Center on 9/11) and the midtown group (those in mid-town Manhattan on 9/11). Subjects answered a series of questions about their memories of 9/11 as well as of distinct, autobiographical memories-in this case, memories of their 2001 summer. The latter served as a baseline memory for evaluating the nature of 9/11 memories. In providing written responses to these questions, subjects were placed in a functional magnetic resonance imaging (fMRI) scanner. The scanner allows researchers to detect brain activity while subjects are retrieving memories.
The written responses revealed that the average number of words in the written descriptions of 9/11 memories for the downtown group was greater than that of the midtown group. However, there was no difference between groups in the number of words used to describe their 2001 summer memories. In addition, comparison within groups revealed that the downtown group used more words to describe 9/11 memories than summer memories while there was no difference across those in the midtown group.
In addition, two judges, blind to the research topic, rated each written memory for amount of detail on a scale from 0 (low level of detail) to 2 (high level of detail). Rating of detail for memories of 9/11 was higher for the downtown group than the Midtown group. There was no difference between groups in the ratings of detail of summer memories. Ratings of detail for 9/11 memories were higher than for summer memories in the downtown group, but did not differ for the midtown group.
The fMRI results were consistent with the written responses. Neural circuits previously shown to be related to an increase in the recollective experience of emotional stimuli learned in a controlled laboratory setting were engaged during retrieval of 9/11 memories in subjects who were close to the World Trade Center on that day. Specifically, an increase in amygdala activity during retrieval of 9/11 events were related to the participants’ proximity to the World Trade Center.
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